I have a friend who has a simulator in his apartment building and we have played there a couple of times. Much quicker than a real round because you aren't walking/riding to your ball.
However, I always score better on the simulator than real life. You very rarely get bad bounces on the course. You are hitting off a mat, which is more forgiving because fat shots still fly a reasonable distance. Your lie is always good (hitting out of the rough or from the fairway is the same). For whatever reason, you rarely hit that one branch six inches wide like you do in real life. And we always just took two putts on the green and moved on. Easier than putting on a simulator.
What you should use it for is grooving a decent swing